Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $194.26   3.622%   $201.2961   $201.30   $201.30   $201.30  
  Purchase #2 $25.26   6.274%   $26.8448   $26.84   $26.85   $26.80  
  Purchase #3 $119.50   5.771%   $126.3963   $126.40   $126.40   $126.40  
  Purchase #4 $93.26   10.426%   $102.9833   $102.98   $103.00   $103.00  
  Purchase #5 $48.84   3.797%   $50.6945   $50.69   $50.70   $50.70  
  Purchase #6 $227.98   8.168%   $246.6014   $246.60   $246.60   $246.60  
  Purchase #7 $115.37   9.849%   $126.7328   $126.73   $126.75   $126.70  
  7 purchase totals = $824.47       $881.5492   $881.54   $881.60   $881.50